A multimedia broadcast and multicast service (MBMS) that provides a broadcasting service to a mobile phone in a 3rd Generation Partnership Project (3GPP) wireless communication system has been standardized in various groups of the 3GPP.
Such a 3GPP wireless communication system includes a wideband code division multiple access (WCDMA) system and a single carrier frequency division multiple access (SC-FDMA)-based long term evolution (LTE) system.
The MBMS is divided into a broadcast service and a multicast service, and only the multicast service may be charged.
In the case of the multicast service, the UE in a given cell is asked whether to use an MBMS. Then, when the UE responds to more than a predetermined number of services, the MBMS is provided to the UE through a secondary common control physical channel (S-CCPCH), and when the UE responds to less than the predetermined number of services, the MBMS is provided to the UE through a dedicated physical channel (DPCH) for efficient radio resource management.
When no UE requests the MBMS, a service is not provided.
When the UE requests receiving the MBMS, the UE needs to perform a random access. When performing the random access, the UE randomly requests access from a base station, and therefore may experience collision with another UE that uses the same preamble code.
In order to minimize such a collision, a controlling radio network controller (CRNC) manages a conventional counting process as shown in FIG. 1.
FIG. 1 shows dataflow in a conventional counting process between a CRNC and a UE in a wireless communication system.
As shown in FIG. 1, in the conventional counting process, a CRNC 20 that manages cells sends a signal to provide an initial access probability factor to the UE 10 in the cell, in step S12.
When receiving the initial access probability factor, the UE 10 attempts a random access by using a proper access probability factor according to a current state of the UE 10, in step S14.
When new counting process is required, the CRNC 20 calculates an optimal access probability factor in step S16, updates the access probability factor with the calculated access probability factor, and transmits the updated access probability factor to the UE 10 by sending a signal thereto, in steps S20 to S22.
The UE 10 receives the updated access probability factor and attempts a random access by using the updated access probability factor, in step S24.
When the UE 10 accesses the CRNC 20 by performing the random access in step S26, the CRNC 20 performs the counting process according to the access of the UE 10 in step S28 and stores counted information in step S30.
Therefore, the CRNC needs to set the initial access probability factor and the optimal access probability factor properly such that the counting process consumes a proper period of time and an accurate counting result can be acquired.
When the CRNC sets the access probability factor high so as to generate collision between UEs that attempt random access or when the CRNC sets the access probability factor low in a situation that few UEs attempt the random access, the counting process consumes a much longer time than normal random access.
A conventional random access preamble P(i) used in the 3GPP WCDMA system is formed by a product of a gold sequence GNi and a signature sequence Ci, and it can be represented as given in Math Figure 1. Herein, the number of random access preamble symbols is denoted as n (n=4096 chips in the WCMDA system).
A 3GPP long term evolution (LTE) system uses a single carrier frequency division multiple access (SC-FDMA), and a random access preamble P(i) used in the SC-FDMA also can be represented as given in Math Figure 1. However, n in the SC-FDMA denotes the number of time domain sampling symbols.
When the signature sequence is generated as a Hadamard sequence with a length of m, the signature sequence can be represented as given in Math Figure 2.
Then, the UE randomly selects a signature sequence according to a state of the UE.P(i)=GNi*Ci  [Math Figure 1]
Where i=0, 1, 2, . . . , n−1, and n is a natural number.Ci=Hm(i%m)  [Math Figure 2]
Where i=0, 1, 2, . . . , n−1, and n is a natural number, and m=16.
In this case, the Hadamard sequence can be defined as given in Math Figure 3.
                                          H            0                    =                      (            1            )                          ⁢                                  ⁢                                            H              k                        =                          (                                                                                          H                                              k                        -                        1                                                                                                                        H                                              k                        -                        1                                                                                                                                                        H                                              k                        -                        1                                                                                                                        -                                              H                                                  k                          -                          1                                                                                                                                )                                ,                                          ⁢                      k            ≥            1                                              [                  Math          ⁢                                          ⁢          Figure          ⁢                                          ⁢          3                ]            
When UEs simultaneously attempting random access select the same signature sequence, collision is generated between the UEs and the random access fails. When the UEs select different signature sequences, the random access can be successfully performed.
However, it is difficult to determine whether a UE performs a random access for using MBMS by only using the signature sequence in the conventional wireless communication system. In addition, when the random access is performed for MBMS counting, a signal for controlling a random access for a different purpose can be transmitted to the UE that performs the random access for using the MBMS, such that the UE performs the random access for the different purpose, which may have a low random access probability factor.
The gold sequence GNi of Math Figure 1 can be generated by using two maximal length sequences (m-sequences) x and y among m-sequences in two primitive polynomials as given in Math Figure 4. The primitive polynomial forming the sequence x can be represented as given in Math Figure 4.X25+X3+1  [Math Figure 4]
In addition, the primitive polynomial forming the sequence y can be represented as given in Math Figure 5.X25+X3+X2+X+1  [Math Figure 5]
An initial value of the sequence x of Math Figure 4 has a scrambling code of xn(0)=n0, xn(1)=n1, . . . , xn(22)=n22, xn(23)=n23, and xn(24)=1, and the sequence y of Math Figure 5 has an initial value of y(0)=y(1)=, . . . , =y(23)=y(24)=1.
A gold sequence Zn generated by using the sequences x and y can be represented as given in Math Figure 6.Zn(i)=xn(i)+y(i)modulo 2, for i=0, 1, 2, . . . , 225−2  [Math Figure 6]
In addition, a real number value of the sequence zn can be calculated as given in Math Figure 7, and GNi=Zn(i).
                                          Z            n                    ⁡                      (            i            )                          =                  {                                                                                                                                        +                        1                                                                                                                                      if                          ⁢                                                                                                          ⁢                                                                                    z                              n                                                        ⁡                                                          (                              i                              )                                                                                                      =                        0                                                                                                                                                -                        1                                                                                                                                      if                          ⁢                                                                                                          ⁢                                                                                    z                              n                                                        ⁡                                                          (                              i                              )                                                                                                      =                        1                                                                                            ⁢                                                                  ⁢                                                                  ⁢                for                ⁢                                                                  ⁢                i                            =              0                        ,            1            ,            …            ⁢                                                  ,                                          2                25                            -              2                                                          [                  Math          ⁢                                          ⁢          Figure          ⁢                                          ⁢          7                ]            
Where n is determined by a scrambling code used by a Node B (i.e., base station) and a signature sequence used by the UE, and therefore the gold sequence does not indicate whether or not it is dedicated to an MBMS.
That is, a preamble of the conventional system does not specify MBMS counting and non-MBMS counting. Therefore, the conventional wireless communication system must analyze a proper random access probability factor during the MBMS counting process and transmit the analyzed random access probability factor to the UE by using a signal. That is, the conventional system complicates the counting process by generating an unnecessary signaling process and insufficiently performs an MBMS counting process.
The above information disclosed in this Background section is only for enhancement of understanding of the background of the invention and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.